The long-term objectives of this project are to use the data of comparative neuroanatomy, neurophysiology and neuropsychology to: (1) reconstruct the evolutionary history of the visual system; and (2) understand the relationship between structure and function within the visual system. The rationale for studying visual information processing in the nervous systems of non-mammalian vertebrates is that by understanding the general mechanisms of such processing, common to amniotes (and perhaps all vertebrates), we may gain insights in mechanisms of vision in humans that might not otherwise be available from experiments limited to the traditional subjects of such research, i.e., rats, cats and monkeys. The subjects of this research are pigeons, since birds are highly specialized for vision. The first phase of the research is to map the extent of the visual system using methods of retrograde and anterograde degeneration. The next phase is to use the techniques of psychophysics and sensory scaling to describe the effects of selective lesions in cell groups of the visual system. The third phase consists of attempts to unravel the mechanisms of deficit and sparing after visual system injury by using tests of attention and perception that involve relational properties of stimuli and modes of information processing.